Preliminary Optimization Of The Polarizable Bond-dipole-based Force Field

Accurate description of intramolecular and intermolecular interactions is the basis for molecular dynamics simulations.The accuracy of the potential energy surface description of molecular systems also determines the reliability of the simulations results.Aiming at the molecular simulation of biomolecules and small organic molecules,many molecular force field models have been proposed.The pre-developed model of polarizable bond-dipole-based force field method has successfully applied in evaluating the interaction energies of the equilibrium dimers such as polypeptide-polypeptide,polypeptide-base,base-base,water-water,etc.However,like other commonly used force field methods,this method still has some defects such as low simulation accuracy in calculating the interaction on non-equilibrium configurations.In this dissertation,based on the polarizable dipole-dipole interaction model,14 single hydrogen-bonding complexes composed by water,methylamine,methanol,peptide,and pyridine molecules were selected as the research object to compose a complexes database,which containing 456 different hydrogen bonding configurations,by changing the hydrogen bond lengths and corresponding angles.The force field parameters were also re-optimized based on this database.In addition,in this paper also takes water molecules as example,and initially attempts to fit the intramolecular terms parameters.The new intermolecular interaction term parameters were then applied to the prediction of the intermolecular interaction energies of 13 equilibrium structures which containing N-H···O(sp³)?O-H···N(sp³),or O-H···N(sp²)types hydrogen bonds and 24 non-equilibrium structures which containing O-H···O(sp²),O-H···O(sp³),or O-H···N(sp²)types hydrogen bonds.The results shown that,comparing with the interaction energies at CCSD(T)/CBS level,the newly parameterized PBFF force field can predict the intermolecular interactions within these structures accurately.The accuracy is comparable to that of M06-2X/cc-p VTZ and MP2/cc-p VTZ methods.The new PBFF force field method was also further applied to the prediction of the interaction energy of the larger dimers,the results indicated that the predicted interaction energies by using this polarizable molecular force field method is significantly better than that using AMBER99SB or AMOEBAPRO13 force field.The revised intramolecular terms and corresponding force field parameters for water molecule determined in this dissertation are also applied to 50 random H₂O clusters which generated by a molecular dynamic simulation.The results shown that the relative energy calculated by this method is consistent with the high-precision ab initio method and obviously better than AMBER99SB,OPLS-AA,or AMOEBAPRO13 force fields.In terms of computational efficiency,this revised polarizable bond-dipole-based force field method is cheaper than the AMOEBA or AMBER force fields.Above all,the revised polarizable bond-dipole-based force field developed in this dissertation can not only accurately and efficiently calculate the interaction energies of the equilibrium hydrogen bonded,but also improve the calculation accuracy of the interaction energies of the non-equilibrium structures.That is,the description of the potential energy surface of the hydrogen bonded systems is more precise.This laid a good foundation for the further development of this method.